The war in the Balkans (1991-1999) demonstrated dramatically the European dependence on the United States in military issues. The EU was paralyzed by the events in the Balkans and showed a startling incapacity to deal with this crisis. Even in 2005, some critics argue that, though the European Union (EU) has become an economic superpower, it is still a negligible player in the realm of security and defense issues. This thesis demonstrates that since 1998 the EU has developed a credible security and defense policy and the capabilities and the mindset successfully to conduct military missions. The thesis argues that the EU forces, EUFOR, will successfully implement the 1995 Dayton Accords in Bosnia and Herzegovina in the wake of NATO's Implementation and Stabilization Forces (IFOR/SFOR). Following an overview of the development of the European Security and Defense Policy (ESDP), the thesis highlights how the ESDP was put into practice for the first time during operation CONCORDIA in Macedonia in 2003. The thesis further examines the challenges that EUFOR has to face in Bosnia and Herzegovina today and it outlines the ways and means that the EU and EUFOR chose to deal with the challenges in the country. The thesis summarizes the findings to show how they support the argument that EUFOR will successfully implement the Dayton Accords and the implications of the topic for ESDP more generally.